I think, in theory, these sound like a reasonable idea for a lot of students, but of course if they are rushed in they will fail. Also, it will be interesting to see if employers actually value them- if they are just pass/fail, they may not be very useful to employers. Some of the subject areas also sound quite broad/vague, so people completing them may not have the specific skills needed to succeed in a particular industry.
I agree that the work placements could cause issues, and yes, some employers expect a 16yo on a work placement to know everything about the world of work already- clearly the point of a work placement is to support and teach them this. 45 days is a decent length placement- so if an employer is willing to put in some work initially, they may well get some useful hours out of the person by the end of the placement.
However, I've also supervised work placement/work experience students in an animal care setting. I'd say 75% of the placements worked well- the student got something out of it, and the business did too. For the other 25%, mostly the placements failed because students just stopped turning up for whatever reason, and I can see why this might put a small employer off accepting another student.
Personally, I think that for students wanting a vocational route, the best thing to do is to enable them to get industry specific exams. I think the equestrian industry has got this right to an extent- many employers respect the BHS exam system- or at least find it a useful indicator of someone's skill level. Many colleges offer this alongside other vocational industry training, and many apprentices can also access the exams. It's not perfect, and it has flaws, but candidates come out with a recognised qualification which will help them get work in the industry. It works, IMO, because it's very specific, so an employer can look at someone with, say, their stage 2, and say, well this shows this person can do X,Y,Z and has A + B theoretical knowledge.
I don't think a broad, vague qualification in "agriculture, environment and animal care" will have the same appeal.